1. Field of the Invention
The present invention relates to novel N,N'-disubstituted bis(maleimides) containing a diorganopolysiloxane linkage in their molecular structure, and to a process for preparing such N,N'-bis(maleimides) from maleic anhydride and amines containing a diorganopolysiloxane linkage.
2. Description of the Prior Art
Certain N,N'-disubstituted bis(maleimides) are useful, in particular, for the preparation of heat-stable polyimides. Poly(amide-imides) or linear polyimides containing a diorganopolysiloxane group in their molecular structure, which are manufactured by reacting a tetracarboxylic acid dianhydride or a tricarboxylic acid monoanhydride with, for example, alpha, omegabis(aminophenoxyalky)diorganopolysiloxanes, are known to this art (see U.S. Pat. Nos. 4,011,279 and 4,395,527). Also known (see British Patent No. 2,137,644) are N,N'-bis(maleimide)siloxanes of the general formula: ##STR2## in which R denotes a hydrogen atom, an alkyl radical or a phenyl radical and n is a number ranging from 1 to 6, which are produced by reacting maleic anhydride with alpha, omegabis(aminophenoxy)diorganopolysiloxanes having from 1 to 6 ##STR3## groups; these bis(maleimides) contain in their structure Si--O--C links which, as a result of their poor strength, tend to limit the possible applications thereof.